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Roig, M. G.; Bello, J. F.; Moreno Vega, M. A. De; Cachaza, J. M.; Kennedy, J. F.
doi: 10.1002/jctb.280490202pmid: 1366915
A physical method for immobilization of liver alcohol dehydrogenase (ADH) by hydrophobic adsorption onto a supporting membrane of polyvinylidene difluoride (PVDF) was performed. Simultaneously, a physicochemical characterization of the immobilized enzyme regarding its kinetic behaviour was performed. The activity/pH profile observed points to an effect of pH on activity that is completely different from the case of ADH in solution. The disturbance in the typical bell‐shaped profile owing to the fact that the enzyme was immobilized is explained on the basis of a potent limitation to the diffusion of the protons in the support. The findings of the present work also reveal the existence of an effect that limits free external diffusion of the substrate towards and/or the product from the support; this effect seems to be the determinant of the overall rate of the enzymatic reaction and is thus of great importance in the effective kinetic behaviour (v([S])) of immobilized ADH, whose kinetic behaviour is complex (non‐Michaelian), as may be seen from the lack of linearity observed in the corresponding double reciprocal and Eadie‐Hofstee plots. By non‐linear regression numerical analysis of the v([S]) data and application of the F‐test for model discrimination, the minimum rate equation necessary to describe the intrinsic kinetic behaviour ofPVDF‐immobilized ADH proved to be one of the polynomial quotient type of degree 2:2 (in substrate concentration).
doi: 10.1002/jctb.280490203pmid: N/A
A model has been developed to describe the performance of a packed‐bed coimmobilized biochemical reactor. Each step in the consecutive reaction is assumed to follow Michaelis—Menten type kinetics. The model includes all the limiting steps controlling the rate of reaction and the additional effect of axial dispersion of bulk liquid. The model equations are solved by the explicit finite difference method from the transient to steady‐state condition. The effects of various parameters of physical importance on the reactor performance are discussed.
Schlicher, Laura R.; Cheryan, Munir
doi: 10.1002/jctb.280490204pmid: N/A
Lactic acid model solutions and fermentation broths were concentrated using a tubular thin‐film composite reverse osmosis membrane. Flux increased linearly with applied transmembrane pressure and was relatively unaffected by flow rate. Osmotic pressures of 1% lactate solutions were 280–560 kPa, depending on the pH or degree of dissociation. Rejections increased with applied pressure. Higher pH caused a slight decrease in flux (due in part to the higher osmotic pressure) and a significant increase in rejection. Above pH 5·6, rejections of lactate and residual sugars were > 97%. In contrast, with cellulose acetate membranes, flux was generally lower and lactate rejection was proportional to the degree of dissociation at lower pressures.
Sharma, Shreekumar N.; Chandalia, Sampatraj B.
doi: 10.1002/jctb.280490205pmid: N/A
The liquid‐phase oxidation of p‐cresol and substituted p‐cresols by air under alkaline conditions using cobaltous chloride as a catalyst and methanol as solvent, has been investigated with a view to obtain the corresponding aldehydes with sufficiently high selectivities. In the case of p‐cresol, the effects of various process parameters on the reaction rate and selectivity with respect to the aldehyde have been investigated. The results obtained are likely to be useful for the development of processes for the production of industrially relevant products such as 4‐hydroxybenzaldehyde, vanillin and syringaldehyde by using p‐cresol as the starting material. Various alternative process schemes have been proposed and evaluated.
Gattinger, Loni D.; Duvnjak, Zdravko; Khan, Waheed A.
doi: 10.1002/jctb.280490206pmid: N/A
For the enzymatic saccharification of canola meal by enzyme preparations from Trichoderma reesei as well as by commercially available hemicellulase and multienzyme preparations, a pretreatment consisting of autoclaving is necessary. These enzyme preparations hydrolysed over 20% (w/w) of pretreated canola meal, which constitutes over 70% saccharification of the total polysaccharides present in canola meal. The results show that saccharification of canola meal is mainly brought about by hemicellulases capable of degrading arabinogalactan, arabinoglucan, galactan and galactomannan, while cellulases and xylanases play a minor role. These hemicellulases were found to be more stable at 50°C than cellulases or xylanases. This pretreatment also released water‐soluble polysaccharides consisting mainly of arabinose and glucose. Trichoderma reesei was unable to produce enzymes capable of hydrolysing this polysaccharide when cultivated on canola meal as substrate.
doi: 10.1002/jctb.280490207pmid: N/A
Silica gels were obtained by drying the silica hydrogels formed at pH values between 1 and 4 at 100°C. The bulk density of the 2–3 mm diameter fraction decreased from 0·62 g cm−3 to 0·20 g cm−3 as the preparation pH increased from pH 3 to pH 3·65. The apparent density of silica gels was between 1·43 and 1·95 g cm−3. Isotherms for the adsorption of water vapour on samples prepared at different pH values showed hysteresis in all cases. Thermogravimetry analysis showed that the amount of bound water was in the range of 4·4 to 5·5% on a dry weight basis. Specific heats were determined by a differential scanning calorimetry method using a sapphire standard and were between 0·82 and 0·97 J g−1 K1.
Koilpillai, Leena; Gadre, Rohini A.; Bhatnagar, Shubra; Raman, Rajan C.; Ponrathnam, Surendra; Kumar, Kamalesh K.; Ambekar, Gangadhar R.; Shewale, Jaiprakash G.
doi: 10.1002/jctb.280490208pmid: 1369290
Macroporous weak cation‐exchange methacrylate polymers were synthesized for the immobilization of penicillin G (Pen G) acylase. The role of certain factors such as pore‐generating solvent, cross‐linking agent, cross‐linking density, and comonomer, in enzyme adsorption and expression was studied. Kerosene was a superior pore‐generating solvent to paraffin oil. Ethylene glycol dimethacrylate and acrylic acid served as the best cross‐linking agent and comonomer, respectively, in the systems studied. 80·3% of the activity of the enzyme adsorbed onto polymer beads prepared with 0·05 mol of acrylic acid (polymer PM‐39) was expressed. Properties of the Pen G acylase, immobilized on PM‐39 by adsorption and cross‐linking with glutaraldehyde (IME‐PM‐39) were studied. The optimum pH, optimum temperature and Km of Pen G acylase shifted from 8·0 to 7·5‐7·8, 50°C to 55°C and 0·038 mol dm−3 to 2·4–3·0 mol dm−3, respectively, as a result of immobilization on PM‐39. IME‐PM‐39 was used repeatedly for 15 cycles in the production of 6‐amino penicillanic acid (6‐APA).
Awadalla, Farouk T.; Habashi, Fathi; Pag, Michel
doi: 10.1002/jctb.280490209pmid: N/A
Chrysotile asbestos (Grade 7RF66) sorbs phosphate ion from aqueous solution of phosphoric acid, basic disodium phosphate, ammonium dibasic phosphate, sodium pyrophosphate, or sodium tripolyphosphate. The amount sorbed varies from 0·2 to 2·5% P2O5. The fiber treated with ammonium dibasic phosphate has appreciably low toxicity that is comparable to chrysophosphate obtained by the reaction of chrysotile asbestos with POCl3 gas, provided the latter is washed thoroughly with water to remove watersoluble ingredients.
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